The present invention relates generally to photovoltaic cell structure. More particularly, the present invention provides a method and structure of a photovoltaic cell for manufacture of solar module using a thin film process. Merely by way of example, the present method and structure have been implemented using a multijunction configuration, but it would be recognized that the invention may have other configurations.
From the beginning of time, human beings have been challenged to find way of harnessing energy. Energy comes in the forms such as petrochemical, hydroelectric, nuclear, wind, biomass, solar, and more primitive forms such as wood and coal. Over the past century, modern civilization has relied upon petrochemical energy as an important source. Petrochemical energy includes gas and oil. Gas includes lighter forms such as butane and propane, commonly used to heat homes and serve as fuel for cooking. Gas also includes gasoline, diesel, and jet fuel, commonly used for transportation purposes. Heavier forms of petrochemicals can also be used to heat homes in some places. Unfortunately, petrochemical energy is limited and essentially fixed based upon the amount available on the planet Earth. Additionally, as more human beings begin to drive and use petrochemicals, it is becoming a rather scarce resource, which will eventually run out over time.
More recently, clean sources of energy have been desired. An example of a clean source of energy is hydroelectric power. Hydroelectric power is derived from electric generators driven by the force of water that has been held back by large dams such as the Hoover Dam in Nevada. The electric power generated is used to power up a large portion of Los Angeles Calif. Other types of clean energy include solar energy. Specific details of solar energy can be found throughout the present background and more particularly below.
Solar energy generally converts electromagnetic radiation from our sun to other useful forms of energy. These other forms of energy include thermal energy and electrical power. For electrical power applications, solar cells are often used. Although solar energy is clean and has been successful to a point, there are still many limitations before it becomes widely used throughout the world. As an example, one type of solar cell uses crystalline materials, which form from semiconductor material ingots. These crystalline materials include photo-diode devices that convert electromagnetic radiation into electrical current. Crystalline materials are often costly and difficult to make on a wide scale. Additionally, devices made from such crystalline materials have low energy conversion efficiencies. Other types of solar cells use “thin film” technology to form a thin film of photosensitive material to be used to convert electromagnetic radiation into electrical current. Similar limitations exist with the use of thin film technology in making solar cells. That is, efficiencies are often poor. Additionally, film reliability is often poor and cannot be used for extensive periods of time in conventional environmental applications. These and other limitations of these conventional technologies can be found throughout the present specification and more particularly below.
From the above, it is seen that improved techniques for manufacturing photovoltaic cells and resulting devices are desired.